Absorption refrigerating system



Feb. 25, 1964 R. 'e. MINER ETAL ABSORPTION REFRIGERATING SYSTEM FiledFeb. 9, 1961 FIG.2

INVENTORS R. e. ,m N E R E.M.ST/UBBLEFIELD A TTORNEYS United StatesPatent Oflice BJZZfiflZ Patented Feb. 25, 1964 3,122,002 ABSQRPEIQNREFRHGERATWG SYSTEM Robert G. Miner and Edward M. Stubhlefield, LaCrosse, Wis, assignors to The Trane Company, La Crosse, Wis acorporation of Wisconsin Filed Feb. 9, 1961, Ser. No. 83,212 tilaims.(Cl. 62-141) This invention relates to absorption refrigerating systernsand more particularly to controls for such systems.

it is an object of this invention to provide means for starting thevarious parts in sequence responsive to manually closing an electricalcircuit to one of the pumps.

It is another object of the invention to provide means for discontinuingoperation in such a manner that concentration of solution andsolidification is avoided.

It is another object of the invention to delay de-energization of thepump which supplies lubrication until the pumps so supplied have beende-energized.

it is another object of the invention to conduct dilute solution fromthe absorber to the absorber solution recirculating conduits on shutdown of the system to flush out the concentrated solution from theseconduits in order to avoid solidification of concentrated solution inthese conduits.

It is another object of the invention to reduce the steam consumption byproviding controls which operate at reduced loads to reduce the rate offlow of dilute solution from the absorber through the heat exchanger tothe generator.

Other objects and advantages will become apparent as the specificationproceeds to describe the invention with reference to the accompanyingdrawings in which:

FIGURE 1 is a diagrammatic view of the absorption system including thecontrols;

FIGURE 2 is a diagram showing the electrical circuit; and

FIGURE 3 is a partial diagrammatic view showing a modification of theinvention of FIGURE 1.

Referring now to FIGURE 1, the absorption system shown has a singleshell ltl enclosing a condenser 12, a generator 14', an evaporator 16,and an absorber 18. It should be understood that other arrangementsmight be used; for instance, the generator and condenser could be in oneshell and the absorber and evaporator could be in a second shell withconduits therebetween for conducting fluids.

The absorber 1% has a coil 20 supplied with cooling fluid by a pump 22.This cooling fluid is conducted from the coil 2d through a conduit 24 toa cooling coil 26 in the condenser 12. From the cooling coil 26, thecooling fluid passes through a pneumatic valve 28 and thence through aconduit 31 to a cooling tower 332. A portion of the fluid flowing inpipe 24 may by-pass the coil 26 through the conduit 2% according to theposition of the pneumatic valve 28 and a portion of the fluid flowingfrom the valve 28 may flow through conduit 53 through pneumaticallyoperated valve 34 thus by-passing the cooling tower 32. A conduit 35conducts fluid from the valve 34 to the pump 22. A pneumatic temperaturecontroller 36 has a temperature sensitive bulb 37 in temperature sensingrelationship with the fluid in conduit 35 and is connected to a sourceof air pressure 38. Temperature controller 36 transmits its controlpressure to valve 34 through conduit 39. Refrigerant vapor from thegenerator 14 is condensed in condenser 12 by removal of heat throughcooling coil 26.

Various types of refrigerant and adsorbent may be used in the presentmachine. A solution of lithium bromide as an absorbent and water as arefrigerant is satisfactory. Other salt solutions may be used ifdesired.

The term concentrated solution as used herein means a solution which isconcentrated in absorbent.

A solution circulating pump 441 receives solution from the absorber 18through conduit 41, anddischarges the solution into a conduit 42 whichis connected to a spray tree 44 which sprays the solution into theabsorber 18 over the tubes 20.

A pump 46 draws solution from the absorber 18 through a conduit 4-8 anddischargese the solution through a conduit 51} which conducts the fluidto one pass of a heat exchanger 52 from which the fluid flows through aconduit 5 1 to the generator 14.

The solution in the generator is heated by a coil '56 which ispreferably supplied with steam as a heating fluid through valve 5%.Boiling of the solution in the generator causes refrigerant vapors topass into the condenser 12. The concentrated solution flows from thegenerator 14 through conduit "59 to one pass of heat exchanger 52 andthence through conduit 6t} and 61 to the absorber 13. The outlet ofconduit 61 is adjacent the entrance to conduit 4-1 and remote from theentrance to conduit 48 so that the solution flowing in conduit 41 ismore concentrated than the solution flowing in conduit i-i3. Theconduits 41 and 48 may be spaced longitudinally of the shell for thesame reason if desired. In the heat exchanger 52, the dilute solutionpassing from the absorber 7.8 to the generator 14 is heated by theconcentrated solution flowing fom tne generator 14 to the absorber 13.The steam valve 58 is connected to a source of steam 62. A pneumatictemperature controller 64 has a temperature sensitive bulb 65 intemperature sensing relationship with the fluid leaving the evaporatorcoil 63 through conduit 65. The temperature of fluid produced in conduit6'5 is responsive to and is substantially the temperature of theevaporator 16. The fluid circulated through the coil 68 may be water,brine, or other fluid, but for purposes of explanation it will beassumed to be water, and it will be called chilled water. A chilledwater pump 67 is connected to receive chilled water from a refrigerationlead through a conduit 69. After flowing through coil 68, the chilledwater is returned to the refrigeration load through conduit 65. Thetemperature controller 64 is connected to a source of pneumatic pressure7% and transmits control pressure to valve 58. A pressure switch 73 isinterposed in the conduit 72 between the pressure controller 64 and thesolenoid valve SAV. The operation of the solenoid valve SAV and thepressure switch 73 will be more fully described later.

The refrigerant condensed in the condenser 12 flows downwardly throughan opening '74 into the evaporator 16. The evaporator has a floatchamber 76 containing a float switch 77 which opens when the level dropsbelow a predetermined point. A conduit 78 conducts refrigerant from thefloat chamber 7 6 to a refrigerant pump 80. The refrigerant flows fromthe pump 89' through a conduit 82 to a spray tree 83 in the evaporator16. Refrigerant vapor flows from the evaporator 16 to the absorber 18thus causing evaporation and cooling of the refrigerant liquid in theevaporator 1s.

Refrigerant from the conduit 82 is conducted through conduit 34 to thepump 84 to cool and lubricate the working parts thereof, and therefrigerant thus conducted to the pump is returned to conduit 78 throughconduit 86.

Refrigerant from conduit 32 also flows through conduit 88 to pumps 40and as to cool and lubricate the working parts thereof. From pump 40,the refrigerant flows through conduits 91 92, and 78. From pump 46, therefrigerant flows through conduits 94, 92, and 78.

A low temperature cut-out switch 96 has a temperature sensitive bulb 97in the refrigerant in the evaporator 16. Switch 96 initiates a shut downof the machine when the 3 evaporator temperature drops below apredetermined point.

A conduit 98 conducts fiuid from conduit 50 to conduit 42. As will beexplained more fully in connection with the controls, the absorberrecirculating pump 4?; and the condenser water pump 22 are the firstpumps to be de-energized when the machine is shut down. inasmuch as thesolution pump 46 continues to operate for a timed period, a portion ofthe solution delivered by it will flow through conduit 98. This solutionwill flow by gravity downward through pipe 42, then through pump 40 intoconduit 4-1 and finally into the bottom of the absorber 18. The moreconcentrated solution in these conduits and in pump 49 is thus flushedout by the more dilute solution from pump 45 and the danger ofsolidification in th se passageways when the system cools down isavoided. The solution in the spray tree 44 drains by gravity when thepump 48 is de-energized. When the machine is in normal operation, thepressure developed by pump 4-9 opposes flow through conduit 98 so thatthere is substantially no how in this conduit 8.

The control system will now be described with reference to FIGURE 2.Electric power is supplied for the motors of the pumps by power lines99. Electric power is supplied to other controls by power lines 160 andTrill. To put the system into operation, the starting button switch 162is closed thus energizing coil 163 which closes contacts 1&4, 166, and108. Closing of contact it; energizes the chilled water pump motor 11%.Closing of holding contact 166 maintains energization of the line.Closing of contact 168 permits energization of coil iii) upon closing ofpressure switch 73. Pressure switch 73 will be closed when thecontroller 64 indicates the need for cooling the chilled water. Withcontacts 73 and closed, coil lid is energized and contacts 112 and 1 4are closed. Closing of contact 112 energizes the corn denser water pumpmotor 136. Closing of contact 114 enengizes coil 11$ provided there is alevel or" water in sump 76 sufficient to close float switch '77. Contact12%) is normally closed. Energization of coil 113 closes contacts 122and 12d. Closing of contact 122 energizes motor 126 of refrigerant pumpClosing of contact 124 energizes coil 12% which closes contacts 130 and132. Closing of contact 139 energizes motor 134 of solution pump 45.Closing of contact 132 energizes coil 135 provided that the temperatureof the chilled water is not so low that temperature cut-out switch 96 isopen. Coil 136, being energized, closes contacts 138 and 14-0. Closingof contact 138 energizes the motor 14-2 of absorption recirculating pump46. Closing of contact 140 energizes solenoid air valve SAV to permitpneumatic pressure to be transmitted from temperature controller 64 tovalve 53 to open valve 53 and allow steam to enter the coil 56 of thegenerator 14.

Closing of contact 146 also energizes coil 14-4 to close contact 146.Coil 144 and contact 146 form a time delay relay which is instantaneousclosing and time delayed opening.

Closing of contact 146 energizes coil 14-8 which cl ses contact 159 andopens contact 12%. The contacts 129 and 159 are so constructed that theyare overlapping in that contact 12% opens after contact 150 has beenmade. Closing of Contact 159 and opening of contact 120 transfers thesource of power for the coil 118 of the refrigerant pump motor contact122 and the coil 128 of the solution pump motor contactor 13% from theportion of the circuit supplied by the pressure switch 73 directly toone side of the source of control voltage.

A normally open pneumatic valve 151 is connected between conduit Stl andconduit 6% to control the flow of solution from conduit 56 to conduit69. Valve 151i is connected to and receives its control pressure througha conduit 153 which is in fluid communication with conduit 72 at a pointbetween the solenoid air valve SAV and the steam valve 58.

Reference is now made to FIGURE 3 which shows a modification of theinvention in which a rcstrictor 155 is mounted in the conduit 5%. Anormally closed pneu matic valve 156 is mounted in a conduit 157 whichis connected to bypass the restrictor 155 in conduit 50. The flow ofsolution through conduit 50 to the heat exchanger 52. is therefore thesum of the flows through the rcstrictor 55 and the valve 156. Pneumaticvalve 156 is connected to and receives its control pressure throughconduit 153.

As the load on the system varies, the steam valve 53 will be modulatedby the controller 64 to maintain an equilibrium at which the steamsupplied to the generator is just sufiicient to provide refrigerationequal to the system load.

With operation at reduced load, refrigerant is absorbed in the absorber18 at a reduced rate and the generator 14 is only required to evaporaterefrigerant at a reduced rate. Under these conditions, economy in theuse of scam is effected by reducing the rate of solution llow to thegenerator 14, because an appreciable amount of heat input is consumed inraising the temperature of the solution leaving the exchanger to theboiling tcniperature in the generator 14.

To accomplish this reduction in the rate of solution flow the valve 151is caused to modulate toward its open position as the reduction or" loadoccurs as measured by the controller 64. In this manner, the rate ofcirculation of solution between the absorber 18 and the generator 14does not substantially exceed the amount required to producerefrigeration equal to the load on the system.

The operation may also be described in the following manner. When theload on the system decreases below a predetermined percentage of fullload, the normally open valve 151 starts to open and dilute solutionllows from conduit to conduit 61} because the pressure is higher inconduit 59 than in conduit 60. Therefore the rate of solution flow tothe generator 14- is reduced. With less solution to be heated to boilingtemperature in the generator more of the heat from the steam isavailable for refrigeration and the evaporator tends to produce a lowertemperature. However, the controls reduce the steam input to maintainthe desired evaporator temperature.

It should also be pointed out that the absorber will operate moreefiiciently because the rate of flow of warm solution from the generatorhas been reduced. For a typical system, the valve 151 may start to openat 75 percent of full load and it may be fully open at 50 percent offull load.

Reference is now made to the system of FIGURE 3. When the load on thesystem decreases below a predetermined percentage of full load, thenormally closed pneumatic valve 156 starts to close thus reducing theflow of solution to the generator 14. The steam required by thegenerator is reduced for the reasons explained above :with reference tothe system of FIGURE 1. In a typical system the valve 156 may start toclose at 75 percent of full load and may be fully closed at 50 percentof full load.

When the chilled water temperature drops below a predetermined figurepressure switch 73 will open to interrupt the circuit to the coils tode-energize the condenser water pump and to interrupt the circuit tocoil 136, the solenoid air valve SAV and the time delay coll 144. Theabsorber recirculating pump motor 142 is thus deenergized; the solenoidair valve SAV closes the steam valve 58 by closing off its air supply.Contact 146 will remain closed for approximately 10 minutes. During thisperiod the contact remains closed and energizes coils 118 and 128 tocontinue to energize the motor 126 of the refrigerant pump and the motor134 of the solution pump.

During the time delay period a small amount of solution from conduit 48flows through the conduit 93 to the conduit 42, thus diluting the moreconcentrated solution in conduit 42, pump 4%, and conduit 41 asexplained above. The continued operation of the pump 46 during the timedelay period also transmits solution from the absorber 13 to thegenerator 14 and solution flows from the generator 14 to the absorber 13thus reducing the concentration of absorbent in the solution in thegenerator 14, the conduit 59, the heat exchanger 52 and the conduit 60.

Should the temperature of the evaporator through abnormal operationbecome dangerously low, the low temperature cut-out 96 will open thecircuit to the coil 136 which de-energizes the absorber recirculatingpump motor 142 by opening the contact 138. At the same time, contact 140will open to tie-energize solenoid air valve and coil 144 of the timedelay relay. As explained previously, the coil 148 will remain energizedthrough the delaying action of coil 144 and contact 146. Therefore, thecontact 150 will remain closed for the time delay period to continueoperation of the refrigerant pump motor 126 and the solution pump motor134 as explained above. When solenoid 1 48 becomes de-energized, contact120 will close and contact 159 will open and inasmuch as these contactsare overlapping, coil 118 and coil 128 will continue to be energized andpump motors 126 and 134 will continue to be energized.

Loss of refrigerant in the evaporator for any reason will result ininsufficient level in the float chamber 76 to maintain the float switch'77 closed. The opening of float switch 77 will de-energize pump motors126, 134, and 142 and solenoid valve SAV thus interrupting thetransmission of pneumatic pressure to valve 58 and causing valve 58 toclose.

Each of the circuits to the motors lit), 116, 126, 134, and 142 has anoverload coil 152 which will open a normally closed contact 154 in thecircuit to the coil which controls the contacts for energizing. theparticular motor.

Although we have described specific embodiments of our invention, it iscontemplated that various changes may be made without departing from thespirit of our invention, and we desire to be limited only by the claims.

We claim:

1. In an absorption refrigerating system, the combination of anabsorber, an evaporator, a generator and a condenser, a pump forcirculating solution from the absorber to the generator, conduit forconducting solution from the generator to the absorber, a conduit forconducting heating medium to the generator, a first valve for regulatingthe flow of heating medium in said conduit, a second valve forregulating the rate of circulation of solution by said pump, and meansfor controlling said first valve and said second valve in response to atemperature produced by said evaporator.

2. In an absorption refrigeration system, the combination of anabsorber, an evaporator, 'a generator and a condenser, a pump forcirculating solution from the absorber to the generator, conduit forconducting solution from the generator to the absorber, means forcontrolling the capacity of the system, said last mentioned meanscomprising a first control member in a solution line to regulate therate of flow of solution circulating through said pump, means forcontrolling the operation of said first control member in response to atemperature produced by said evaporator, [a second control member forcontrolling the rate of flow of heating medium to the generator, andmeans responsive to a temperature produced by the evaporator forcontrolling the operation of said second control member.

3. In an absorption refrigerating system, the combination of anabsorber, an evaporator, a generator and a condenser, a heat exchanger,a first conduit for conducting dilute solution from the absorber to afirst pass or the heat exchanger, a second conduit for conductingsolution from the first pass of the heat exchanger to the generator, athird conduit fior conducting concentrated solution from the generatorto a second pass of the heat exchanger, a fourth conduit for conductingsolution from the second pass of the heat exchanger to the absorber, apump in said first conduit for pumping solution in said first conduitfrom said absorber to the first pass of the heat exchanger and means forconducting solution from said first conduit at a point between the pumpand the heat exchanger bacl; to said absorber without passing throughthe heat exchanger, and means in said last mentioned means forregulating the flow therein responsive to a temperature produced by theevaporator.

4. In an absorption refrigerating system, the combination of anabsorber, an evaporator, a generator and a condenser, a heat exchanger,a first conduit for conducting dilute solution from the absorber to afirst pass of the heat exchanger, a second conduit for conductingsolution from the first pass of the heat exchanger to the generator, athird conduit for conducting concentrated solu tion from the generatorto a second pass of the heat exchanger, a fourth conduit for conductingsolution from the second pass of the heat exchanger to the absorber, apump in said first conduit for pumping solution in said first conduittrom the absorber to the generator, valve means in said first conduitfor controlling the flow in said first conduit, and means forcontrolling said valve in response to a temperature produced in saidevaporator.

5. In an absorption refrigerating system, the combination of anabsorber, an evaporator, a generator and a condenser, a heat exchanger,a first conduit for conducting dilute solution from the absorber to afirst pass of the heat exchanger, a second conduit for conductingsolution 7 from the first pass of the heat exchanger to the generator, athird conduit for conducting concentrated solution from the generator toa second pass of the heat exchanger, a

fourth conduit for conducting solution from the second pass of the heatexchanger to the absorber, a pump in said first conduit for pumpingsolution in said first conduit from said absorber to the generator, flowrestricting means and valve means connected in parallel flowrelationship in said first conduit, and means for controlling said valvemeans in response to a temperature produced in said evaporator.

References Qited in the file of this patent UNETED STATES PATENTS2,502,104 Reid Mar. 28, 1950 3,002,359 Miner Oct. 3, 1961 3,005,318Miner Oct. 24, 1961

1. IN AN ABSORPTION REFRIGERATING SYSTEM, THE COMBINATION OF ANABSORBER, AN EVAPORATOR, A GENERATOR AND A CONDENSER, A PUMP FORCIRCULATING SOLUTION FROM THE ABSORBER TO THE GENERATOR, CONDUIT FORCONDUCTING SOLUTION FROM THE GENERATOR TO THE ABSORBER, A CONDUIT FORCONDUCTING HEATING MEDIUM TO THE GENERATOR, A FIRST VALVE FOR REGULATINGTHE FLOW OF HEATING MEDIUM IN SAID CONDUIT, A SECOND VALVE FORREGULATING THE RATE OF CIRCULATION OF SOLUTION BY SAID PUMP, AND MEANSFOR CONTROLLING SAID